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Patented July 6, 1852.

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NATHAN AMES, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO WVALTER BRYENT.

CENTER-SQUARE FOR FINDING THE CENTER OF .A. CIRCLE.

Specification of Letters Patent No. 9,089, dated July 6, 1852.

To all whom it may concern:

Be it known that I, NATHAN Aims, of Saugus, in the county of Essex and State of Massachusetts, have invented a new and useful instrument, called the center-square, for finding immediately the center of any circle or the end of any cylindrical body, in combination with the common tryingsquare; and I do hereby declare that the following is a full and exact description thereof, reference being had to the accompanying drawings and to the letters of reference marked thereon.

The figure represents a perspective view of the instrument.

B A C, cast iron, or metal of any kind, or wood, forming a right angle at A. B C, unites the ends of B A C, and is either cast in the same piece with B A C, or made separate and fastened on to it. A D, steel plate crossing B C to A, (and fastened on) in such a manner, that one edge of it, divides the right angle, A, into two equal angles, and crosses the center of B C at V, so that D W C, and D W B, are right angles. That part of the plate extending from WV to D, for convenience, is graduated into inches and fractional parts of an inch. The size of the instrument may be larger or smaller according to the size of the circles to which it may be applied. The longer the plate, A D, the greater circle it will center.

The method of using the instrument is as follows :To find the centeras also the diameter and radius-of any circle, as for instance the end of a cylinder; place the instrument over the circle, letting the plate, A D, rest upon it; press the angle, A, toward the circle, until the sides, B A, and A C, touch the circle (represented in the figure by the dots). The line, A D, will then be found always to pass directly through the center, dividing the circle into two equal parts. Mark this line with a pointed instrument. Slide the center-square a quarter around, or so, and mark another line as before. The point of intersection of these two lines, will always be the center of the circle, (as seen in Fig. 2).

Since the angles formed by the plate, A D.

dividing any right angle into two equal parts, thereby making it easy to round the corner by putting one foot of the dividers in the dividing line (Fig. The longitudinal center of any right angle parallelogram, as of a table, (Fig. 3) may be readily found by it, the point of intersection of the dotted lines (Fig. 3,) being in the longitudinal center. The graduated plate from TV to D, is, also, handy as a rule.

hat I claim as my invention, and desire to secure by Letters Patent is:

1. The application, to an instrument, sub stantially in the manner herein set forth, of a geometrical fact, viz, that any circle, touching the sides of a right angle, will be divided into two equal parts by the line which divides the right angle into two equal parts.

2. The union of the above with the common trying square by means of the bar B, C, as described.

NATHAN AMES.

Vitnesses IRAH CHASE, Jr., WM. HONEYBUN. 

